The present invention relates to a connecting piece including a waveguide section for connecting a rectangular waveguide and a waveguide with an approximately elliptical cross section.
Waveguides with an approximately elliptical cross section have recently found acceptance in practice. These waveguides are designed either as rigid waveguides or as semiflexible waveguides and are constituted by either smooth or corrugated hollow tubes. To connect such a waveguide with an approximately elliptical inner cross section to the normally used standard rectangular waveguides, it is necessary to use an appropriately designed transition piece. This transition piece must have such dimensions that it provides a connection which produces as little reflection as possible over a relatively wide frequency range.
For this purpose it is known to widen the inner cross section of a rectangular waveguide over a length of about 3/4 .lambda..sub.g, .lambda..sub.g being the guide wavelength ##EQU1## OF THE ENERGY TO BE PROPAGATED THEREIN, IN THE DIRECTION TOWARD THE ELLIPTICAL WAVEGUIDE SO THAT THE DESIRED TRANSITION IS PRODUCED IN CONJUNCTION WITH ADDITIONAL MATCHING ELEMENTS. A stepwise enlargement of the rectangular cross section in the direction toward the larger elliptical cross section is also known.
Such transitions, however, are extremely expensive to produce because they require a complicated manufacturing process and they are not suited for mass production. This also applies for waveguide transition pieces having an approximately conical shape in which one or a plurality of recesses are cut in the area of the transition to attempt to produce matching without additional adjustable matching elements.